dialect/sql/schema: add multi schema and view support for schema dump (#4335)

dialect/sql/builder.go

@@ -240,6 +240,80 @@ func (t *TableBuilder) Query() (string, []any) {
 	return t.String(), t.args
 }
 
+// ViewBuilder is a query builder for `CREATE VIEW` statement.
+type ViewBuilder struct {
+	Builder
+	schema  string    // view schema.
+	name    string    // view name.
+	exists  bool      // check existence.
+	columns []Querier // table columns.
+	as      Querier   // view query.
+}
+
+// CreateView returns a query builder for the `CREATE VIEW` statement.
+//
+//	t := Table("users")
+//	CreateView("clean_users").
+//		Columns(
+//			Column("id").Type("int").Attr("auto_increment"),
+//			Column("name").Type("varchar(255)"),
+//		).
+//		As(Select(t.C("id"), t.C("name")).From(t))
+func CreateView(name string) *ViewBuilder { return &ViewBuilder{name: name} }
+
+// Schema sets the database name for the view.
+func (v *ViewBuilder) Schema(name string) *ViewBuilder {
+	v.schema = name
+	return v
+}
+
+// IfNotExists appends the `IF NOT EXISTS` clause to the `CREATE VIEW` statement.
+func (v *ViewBuilder) IfNotExists() *ViewBuilder {
+	v.exists = true
+	return v
+}
+
+// Column appends the given column to the `CREATE VIEW` statement.
+func (v *ViewBuilder) Column(c *ColumnBuilder) *ViewBuilder {
+	v.columns = append(v.columns, c)
+	return v
+}
+
+// Columns appends a list of columns to the builder.
+func (v *ViewBuilder) Columns(columns ...*ColumnBuilder) *ViewBuilder {
+	v.columns = make([]Querier, 0, len(columns))
+	for i := range columns {
+		v.columns = append(v.columns, columns[i])
+	}
+	return v
+}
+
+// As sets the view definition to the builder.
+func (v *ViewBuilder) As(as Querier) *ViewBuilder {
+	v.as = as
+	return v
+}
+
+// Query returns query representation of a `CREATE VIEW` statement.
+//
+// CREATE VIEW [IF NOT EXISTS] name AS
+//
+//	(view definition)
+func (v *ViewBuilder) Query() (string, []any) {
+	v.WriteString("CREATE VIEW ")
+	if v.exists {
+		v.WriteString("IF NOT EXISTS ")
+	}
+	v.writeSchema(v.schema)
+	v.Ident(v.name)
+	if len(v.columns) > 0 {
+		v.Pad().Wrap(func(b *Builder) { b.JoinComma(v.columns...) })
+	}
+	v.WriteString(" AS ")
+	v.Join(v.as)
+	return v.String(), v.args
+}
+
 // DescribeBuilder is a query builder for `DESCRIBE` statement.
 type DescribeBuilder struct {
 	Builder
@@ -3884,7 +3958,7 @@ func (b *Builder) isQualified(s string) bool {
 		ident && !pg && strings.Contains(s, "`.`") // `qualifier`.`column`
 }
 
-// state wraps the all methods for setting and getting
+// state wraps all methods for setting and getting
 // update state between all queries in the query tree.
 type state interface {
 	Dialect() string
@@ -3930,17 +4004,33 @@ func (d *DialectBuilder) Describe(name string) *DescribeBuilder {
 //
 //	Dialect(dialect.Postgres).
 //		CreateTable("users").
-//			Columns(
-//				Column("id").Type("int").Attr("auto_increment"),
-//				Column("name").Type("varchar(255)"),
-//			).
-//			PrimaryKey("id")
+//		Columns(
+//			Column("id").Type("int").Attr("auto_increment"),
+//			Column("name").Type("varchar(255)"),
+//		).
+//		PrimaryKey("id")
 func (d *DialectBuilder) CreateTable(name string) *TableBuilder {
 	b := CreateTable(name)
 	b.SetDialect(d.dialect)
 	return b
 }
 
+// CreateView creates a ViewBuilder for the configured dialect.
+//
+//	t := Table("users")
+//	Dialect(dialect.Postgres).
+//		CreateView("users").
+//		Columns(
+//			Column("id").Type("int"),
+//			Column("name").Type("varchar(255)"),
+//		).
+//		As(Select(t.C("id"), t.C("name")).From(t))
+func (d *DialectBuilder) CreateView(name string) *ViewBuilder {
+	b := CreateView(name)
+	b.SetDialect(d.dialect)
+	return b
+}
+
 // AlterTable creates a TableAlter for the configured dialect.
 //
 //	Dialect(dialect.Postgres).